There are numerous posts out there about being a good speaker, but what about being a good attendee? I've been, and spoke to enough conferences to see what annoy the person on the stage. Since the individual with the mic is giving his time, and his expertise to the attendees, I think it deserves some respect, so here is my list of rules to be a good attendee:
Honor us with your presence
This one is not only for the speaker, but also for the organizers: if you bought a ticket, come to the event. Even more if the ticket was free as in those cases, most of the time, the event will be full: by not coming, you prevent someone who was able, and really wanted to be there to get an entree. It's even more annoying for the speaker to have an empty room, because so many people didn't come. We all have our reason, and last minute's fire to extinguish, but if it's the case, release your ticket or give it to someone else.
Arrive on time
Arrive even before the beginning of the presentation, and give yourself some time for the possible traffic (or public transport), and to register yourself once you are at the venue. Every conference with more than one speaker are on tight schedule: the speaker won't wait for you. That can be disturbing to see people coming into the room, looking for a seat while you are in front telling your story. You'll also miss something important that may help you to understand the rest of the presentation.
Read the abstract
Most conferences, if it's not all, put the abstract of the speaker's presentation on their website, on the agenda, or even give you a paper schedule with the information on: read it. That seems to be stupid, but too often people just read the title, and are disappointed: the talk wasn't what they had in mind. Of course, that could happen even if you read the description of the presentation, but I'm sure you'll save yourself some surprises.
In all my presentations, I ask people to tweet about cool stuff they hear, if they disagree on something, share something they learn or just quote me. Except for taking note, and sharing on your preferred social media (about the conference), listen to the speaker. The person in front of you is giving his time to share his passion with you: you should at least listen. There are some speakers who would also consider tweeting about their presentations as a lack of respect, and not listening: keep this in mind. It's even worst when you are talking with someone else, even if you are whispering. In that situation, you are not just disturbing the presenter, but also people around you who enjoy the presentation, and are missing bites of it because of you. Lastly, put your cellphone on silence mode, and you won't disturb anyone.
Adhere to the law of the two feet
I've done plenty of camp style events, and I really like the informal spirit of those. One thing is the law of two feet: if you feel you are not learning, it's not a topic you have any interest in, or you fall asleep, either because the speaker is boring or not... leave the room! Some speakers would be annoyed by people living the room as you can think it's because of you, but personally, I would prefer that you go learn something elsewhere, then losing your time with me in front of you.
If there are technical problems, let the speaker know
If the speaker isn't talking quite loud, let him know. If the text size for a code demo isn't big enough for the last row, let the speaker know. If you don't understand something, ask for clarification to the person on the stage. In short, don't get frustrated by a situation that can be solved, and let the speaker know. Sometimes the speaker is too much in "presentation mode" that he won't notice it, and hey, guess what, you are the attendee, so you know what is good or not for you.
Ask short questions
Please, please, please, and please: stop asking multiple questions in one sentence or telling your story for 5 minutes by ending it with the question you really want to ask. There is limited time for questions in conferences, and you may not be the only person who has questions. Asking short precise question is the key. If you are too shy to ask your question with all the crowd, please go see the speaker after his talk: every good speaker will stick around after his talk (most of the time outside of the room not to take time from the next speaker) to meet attendees, and answer further questions.
Fill the feedbacks' form/sheet with useful information
I didn't like your presentation mean nothing to me as a speaker. Why you didn't like it? Is it because it wasn't what you expected? Is it because you don't like me or my style as a speaker? Is it because I said something wrong? Nobody is perfect, and feedbacks' form are not useful if you don't give any details. Be precise when you are giving comments. What did you like? What you didn't like, and why? What can be improved? What was wrong? Most of the time, if it's too complex for the feedbacks' sheet, go talk directly to the speaker. Personally, I'm more than welcome to have feedback, if the feedback is constructive.
Say thanks to the speaker
How much time will it take you to go see the speaker, shake his hand, and say "thanks, I liked your presentation"? Maybe, 30 seconds? If you liked the talk, just take 30 seconds to say thanks. As a speaker, even if my company is paying me to speak, I still took my time to share my knowledge, and passion with you. It's always amazing when people tell you they liked what you just did. Do the same with conference organizers!
Respect the one on the stage
I would have been able to summarize my rules in one simple step: respect the one on the stage. If you disagree, be respectful. If you don't like the talk or the speaker, be respectful too. Put yourself in the shoes of the one with the mic, and ask yourself "how would I like the attendees to be during my talk", and act like it.
Even if I think most of those rules should always be respected, of course, they are mine, and cannot apply to all speakers. On that note, I'm usually a laid back speaker, and most of them don't really disturb me, but as I said, at the end, it's a question of respect. Have a good conference!